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PLC concepts made easy
4.4 Memory areas, addressing and data types
Easy Book
Manual, 03/2014, A5E02486774-AF
61
Data types
Description
Array and structure
data types
• Array contains multiple elements of the same data type. Arrays can be created in the block
interface editors for OB, FC, FB, and DB. You cannot create an array in the PLC tags editor.
• Struct defines a structure of data consisting of other data types. The Struct data type can be
used to handle a group of related process data as a single data unit. You declare the name
and internal data structure for the Struct data type in the data block editor or a block interface
editor.
Arrays and structures can also be assembled into a larger structure. A structure can be nested
up to eight levels deep. For example, you can create a structure of structures that contain arrays.
PLC data types PLC Data type is a user-defined data structure that defines a custom data structure that you can
use multiple times in your program. When you create a PLC Data type, the new PLC Data type
appears in the data type selector drop drop-lists in the DB editor and code block interface editor.
PLC Data types can be used directly as a data type in a code block interface or in data blocks.
PLC Data types can be used as a template for the creation of multiple global data blocks that use
the same data structure.
Pointer data types
• Pointer provides an indirect reference to the address of a tag. It occupies 6 bytes (48 bits) in
memory and can include the following information to a variable: DB number (or 0 if the data is
not stored in a DB), memory area in the CPU, and the memory address.
• Any provides an indirect reference to the beginning of a data area and identifies its length.
The Any pointer uses 10 bytes in memory and can include the following information: Data
type of the data elements, number of data elements, memory area or DB number, and the
"Byte.Bit" starting address of the data.
• Variant provides an indirect reference to tags of different data types or parameters. The
Variant pointer recognizes structures and individual structural components. The Variant does
not occupy any space in memory.
Although not available as data types, the following BCD (binary coded decimal) numeric
formats are supported by the conversion instructions.
● BCD16 is a 16-bit value (-999 to 999).
● BCD32 is a 32-bit value (-9999999 to 9999999).